Absorbent paper products, such as paper towels, facial tissues, and other similar products, are designed to include several important properties. For example, the product should have good bulk, a soft feel, and should be highly absorbent. The product should also have good strength even while wet and should resist tearing. Unfortunately, it is difficult to produce a high-strength paper product that is also soft and highly absorbent. Usually when steps are taken to increase one property of the product, other characteristics of the product are adversely affected.
In order to produce such absorbent paper products, it is common to laminate two or more tissue plies in order to produce the final tissue product. A laminated product is typically more flexible and softer when compared to one single ply having a comparative thickness and basis weight. Further, a laminated product is typically provided with better absorbent capacity and bulk.
The lamination of two or more plies is often made by means of gluing. In such products, a mechanical embossing of at least one of the plies is often performed prior to any gluing step.
Typical manufacturing processes include first embossing two paper plies in a three-dimensional structure with alternating raised and recessed portions. After embossing, an adhesive is applied to one of the plies, and the two plies are joined in a press nip between two embossing rolls. This results in the raised portions of the respective plies being adhesived to each other. Similar processes are described in EU Patent Nos. 796,727 and 738,588.
Another process for laminating two paper plies provides each ply being fed over a pattern roll. The pattern rolls are provided with alternating raised and recessed portions. Adhesive is applied to one ply as it traverses over the roll. The two resulting plies are then adhesively bonded together in a nip disposed between the two pattern rolls. The pattern rolls are in register with each other so that a joining and compression of the paper plies occur in a pattern corresponding to the protuberances disposed upon the pattern rolls. Processes like this are described in U.S. Pat. No. 5,443,889.
Alternatively, some processes apply adhesive to a tissue ply disposed in a press nip between a first pattern roll and an impression roll. The ply is eventually laminated to another ply in a press nip between the same impression roll and a second pattern roll having a pattern corresponding with that of the first pattern roll and driven in registry with the first pattern roll. Such processes are disclosed in U.S. Pat. Nos. 3,672,950; 3,867,225; and 7,282,108 B2.
In any regard, significant amounts of adhesive are typically required to bond the various plies together in a multi-ply structure. Traditionally, the entire emboss is coated with an adhesive and then bonded to an adjacent ply. This results in a structure that is significantly stiffer than would be preferred by consumers. Additionally, coating the entire embossment requires the use of significant quantities of adhesive. This results in higher production costs. Net—you are left with a product that is expensive to produce and is not necessarily consumer preferred.
Accordingly, it would be significantly advantageous to provide for the gluing of two adjacent layers of an embossed substrate which reduces the overall amount of adhesive required to complete the emboss process, thereby reducing the cost of manufacturing. This would also increase the favorability of the finally produced product with consumers.